Lead Poisoning

If its a Bosch (most are) then that will be your problem! They tend to go bad pretty fast. The way that AEM told me to check it was to remove the sensor and plug it back up to the harness, soak a rag with gas and wrap it around the sensor. It should peg the gauge pig rich. If not, its faulty.

Most AFR gauges will show 14.7 when the sensor is bad or inoperable and won't change under any condition.